Stratigraphy and Conodont Paleontology of the Salamonie Dolomite and Lee Creek Member of the Brassfield Limestone (Silurian) In Southeastern Indiana and Adjacent Kentucky

Abstract

Zonation established by study of the conodont faunas of the Lee Creek Member (new member) of the Brassfield Limestone and of the Salamonie Dolomite, both of Silurian age, from 42 sections in southeastern Indiana and north-central Kentucky differs from the conodont zonation established by O. H. Walliser in 1964 for the lower Silurian and lower part of the middle Silurian rocks of the Carnic Alps of Europe. Three conodont assemblage zones are named. In ascending order these are the Icriodina irregularis Assemblage Zone, the Neospathognathodus celloni Assemblage Zone, and the Pterospathodus amorphognathoides-Spathognathodus ranuliformis Assemblage Zone. These zones correspond in general with the upper part of Walliser’s Bereich I and with his celloni-and amorphognathoides-Zones. The new name Lee Creek Member is applied to a thin dolomite unit at the top of the Brassfield Limestone. Fifty-nine named species, 16 of them new, belonging to 22 genera, two of them new, were identified from about 8,900 specimens obtained in this study. The new taxa include the genera Diadelognathus and Neospathognathodus and the species Diadelognathus compressus, D. excertus, D. primus, Drepanodus aduncus, Ligonodina petila, Neospathognathodus bullatus, N. ceratoides, N. latus, Ozarkodina hanoverensis, 0. neogaertneri, Spathognathodus hadros, S. polinclinatus, Synprioniodina? variabilis, Trichonodella asymmetrica, T.? expansa, and T. papilio. Two species each of Diadelognathus and of Paltodus, and one each of Carniodus, Distacodus?, and Trichonodella are described but not named.